diff options
| -rw-r--r-- | lib/Transforms/IPO/AddReadAttrs.cpp | 35 | ||||
| -rw-r--r-- | test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll | 10 |
2 files changed, 36 insertions, 9 deletions
diff --git a/lib/Transforms/IPO/AddReadAttrs.cpp b/lib/Transforms/IPO/AddReadAttrs.cpp index 7af071c..5460a5b 100644 --- a/lib/Transforms/IPO/AddReadAttrs.cpp +++ b/lib/Transforms/IPO/AddReadAttrs.cpp @@ -86,17 +86,34 @@ bool AddReadAttrs::runOnSCC(const std::vector<CallGraphNode *> &SCC) { // Scan the function body for instructions that may read or write memory. for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) { - CallSite CS = CallSite::get(&*II); - - // Ignore calls to functions in the same SCC. - if (CS.getInstruction() && SCCNodes.count(CG[CS.getCalledFunction()])) - continue; - - if (II->mayWriteToMemory()) + Instruction *I = &*II; + + // Some instructions can be ignored even if they read or write memory. + // Detect these now, skipping to the next instruction if one is found. + CallSite CS = CallSite::get(I); + if (CS.getInstruction()) { + // Ignore calls to functions in the same SCC. + if (SCCNodes.count(CG[CS.getCalledFunction()])) + continue; + } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) { + Value *Target = LI->getPointerOperand()->getUnderlyingObject(); + // Ignore loads from local memory. + if (isa<AllocaInst>(Target)) + continue; + } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { + Value *Target = SI->getPointerOperand()->getUnderlyingObject(); + // Ignore stores to local memory. + if (isa<AllocaInst>(Target)) + continue; + } + + // Any remaining instructions need to be taken seriously! Check if they + // read or write memory. + if (I->mayWriteToMemory()) // Writes memory. Just give up. return false; - - ReadsMemory |= II->mayReadFromMemory(); + // If this instruction may read memory, remember that. + ReadsMemory |= I->mayReadFromMemory(); } } diff --git a/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll b/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll new file mode 100644 index 0000000..0f63c1a --- /dev/null +++ b/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll @@ -0,0 +1,10 @@ +; RUN: llvm-as < %s | opt -addreadattrs | llvm-dis | grep readnone | count 2 + +declare i32 @g(i32*) readnone + +define i32 @f() { + %x = alloca i32 ; <i32*> [#uses=2] + store i32 0, i32* %x + %y = call i32 @g(i32* %x) ; <i32> [#uses=1] + ret i32 %y +} |